Acoustic wave element, multi plexer, and communication module

Abstract

The acoustic wave element of the present invention includes a multi-mode type filter and a capacitance part. The multi-mode type filter includes a substrate comprised of a piezoelectric crystal; a first IDT to which a signal is input and a second IDT which is adjacent to this, each IDT including a first comb-shaped electrode and a second comb-shaped electrode which is connected to a reference potential, each comb-shaped electrode being located on the upper surface of the substrate and including a plurality of electrode fingers. The capacitance part is located on the upper surface of the substrate and includes a first counter electrode which is electrically connected to the first IDT at the first comb-shaped electrode side, and a second counter electrode which is arranged at a distance from the first counter electrode and is connected to the reference potential.

The invention claimed is: 
     
       1. An acoustic wave element, comprising:
 a substrate comprised of a LiTaO 3  or LiNbO 3  piezoelectric crystal, wherein the substrate comprises an upper surface and a lower surface; 
 a multi-mode type filter comprising a first IDT to which a signal is input and a second IDT which is adjacent to the first IDT, the first IDT comprising a first comb-shaped electrode and a second comb-shaped electrode which is connected to a reference potential, each comb-shaped electrode being located on the upper surface of the substrate and comprising a plurality of electrode fingers; and 
 a capacitance part comprising a first counter electrode which is electrically connected to the first IDT at the first comb-shaped electrode side, and a second counter electrode which is arranged at a distance from the first counter electrode and is connected to the reference potential, each counter electrode being located on the upper surface of the substrate, 
 wherein the substrate and the capacitance part comprise the configuration of (1) or (2):
 (1) in the substrate, a Z-axis of the piezoelectric crystal is directed from the lower surface toward the upper surface of the substrate, but the Z-axis is not perpendicular to the upper surface, and in the capacitance part, the first counter electrode and the second counter electrode are arranged in this order along a forward direction of the Z-axis of the piezoelectric crystal in a plan view of the upper surface of the substrate; 
 (2) in the substrate, the Z-axis of the piezoelectric crystal is directed from the upper surface toward the lower surface of the substrate, but the Z-axis is not perpendicular to the upper surface, and in the capacitance part, the first counter electrode and the second counter electrode are arranged in this order along the forward direction of the Z-axis of the piezoelectric crystal in a plan view of the upper surface of the substrate. 
 
 
     
     
       2. The acoustic wave element according to  claim 1 , wherein an inclination of the direction from the first counter electrode toward the second counter electrode in the capacitance part relative to the direction perpendicular to the direction of propagation of the acoustic wave is 45° or less. 
     
     
       3. The acoustic wave element according to  claim 1 , wherein the direction from the first counter electrode toward the second counter electrode in the capacitance part is perpendicular to the direction of propagation of the acoustic wave. 
     
     
       4. The acoustic wave element according to  claim 1 , further comprising an auxiliary resonator electrically connected to the first comb-shaped electrode of the first IDT, wherein the capacitance part is electrically connected to the multi-mode type filter through the auxiliary resonator. 
     
     
       5. The acoustic wave element according to  claim 1 , wherein a facing width of the first counter electrode and the second counter electrode is longer than the length of the electrode fingers. 
     
     
       6. The acoustic wave element according to  claim 1 , wherein the capacitance part is positioned on the lateral side of the multi-mode type filter in the direction perpendicular to the direction of propagation of the acoustic wave. 
     
     
       7. The acoustic wave element according to  claim 1 , wherein a distance from the center of the width of the first counter electrode to the center of the width of the second counter electrode is larger than a distance between adjacent electrode fingers in the first IDT. 
     
     
       8. A multiplexer, comprising:
 an antenna terminal, 
 a transmitting filter filtering a transmission signal and outputting the result to the antenna terminal, and 
 a receiving filter filtering a reception signal from the antenna terminal, 
 wherein the receiving filter is configured by the acoustic wave element according to  claim 1 . 
 
     
     
       9. A communication module, comprising:
 an antenna, 
 the multiplexer according to  claim 8  which is electrically connected to the antenna, and 
 an RF-IC which is electrically connected to the multiplexer. 
 
     
     
       10. The acoustic wave element according to  claim 1 , wherein a gap between the first counter electrode and the second counter electrode is larger than a gap between the electrode fingers in the first IDT. 
     
     
       11. An acoustic wave element, comprising
 a substrate comprised of a piezoelectric crystal, wherein the substrate comprises an upper surface; 
 a multi-mode type filter comprising a first IDT to which a signal is input and a second IDT which is adjacent to the first IDT, the first IDT comprising a first comb-shaped electrode and a second comb-shaped electrode which is connected to a reference potential, each comb-shaped electrode being located on the upper surface of the substrate and comprising a plurality of electrode fingers; and 
 a capacitance part comprising a first counter electrode which is electrically connected to the first IDT at the first comb-shaped electrode side, and a second counter electrode which is arranged at a distance from the first counter electrode and is connected to the reference potential, each counter electrode being located on the upper surface of the substrate, 
 wherein, in the capacitance part, the first counter electrode and the second counter electrode are arranged in the direction of propagation of the acoustic wave, and the width of the first counter electrode in the direction of propagation of the acoustic wave is larger than the width of the second counter electrode in the direction of propagation of the acoustic wave. 
 
     
     
       12. The acoustic wave element according to  claim 11 , wherein the direction from the first counter electrode toward the second counter electrode is substantially parallel to the direction of propagation of the acoustic wave. 
     
     
       13. The acoustic wave element according to  claim 11 , wherein the second counter electrode is a rectangular shape, and the first counter electrode comprises a first electrode portion and a second electrode portion each comprising a rectangular shape, which are arranged so as to sandwich the second counter electrode therebetween in the direction of propagation of the acoustic wave. 
     
     
       14. The acoustic wave element according to  claim 11 , further comprising an auxiliary resonator electrically connected to the first comb-shaped electrode of the first IDT, wherein the capacitance part is electrically connected to the multi-mode type filter through the auxiliary resonator. 
     
     
       15. The acoustic wave element according to  claim 11 , wherein a facing width of the first counter electrode and the second counter electrode is longer than the length of the electrode fingers. 
     
     
       16. The acoustic wave element according to  claim 11 , wherein the capacitance part is positioned on the lateral side of the multi-mode type filter in the direction perpendicular to the direction of propagation of the acoustic wave. 
     
     
       17. The acoustic wave element according to  claim 11 , wherein a distance from the center of the width of the first counter electrode to the center of the width of the second counter electrode is larger than a distance between adjacent electrode fingers in the first IDT. 
     
     
       18. A multiplexer, comprising:
 an antenna terminal, 
 a transmitting filter filtering a transmission signal and outputting the result to the antenna terminal, and 
 a receiving filter filtering a reception signal from the antenna terminal, 
 wherein the receiving filter is configured by the acoustic wave element according to  claim 5 . 
 
     
     
       19. A communication module, comprising:
 an antenna, 
 the multiplexer according to  claim 18  which is electrically connected to the antenna, and 
 an RF-IC which is electrically connected to the multiplexer. 
 
     
     
       20. The acoustic wave element according to  claim 11 , wherein a gap between the first counter electrode and the second counter electrode is larger than a gap between the electrode fingers in the first IDT.